Effect of florfenicol on selected parameters of immune and antioxidant systems, and damage indexes of juvenile Litopenaeus vannamei following oral administration

• This study evaluated the effect of FLR on the health of L. vannamei.
• FLR caused immunosuppressive effects of cultured shrimp.
• FLR inhibied antioxidant status of cultured shrimp.
• FLR caused biological macromolecular damage of cultured shrimp.

Florfenicol (FLR) is a commonly used antibiotic for the treatment of bacterial diseases in white shrimp Litopenaeus vannamei. The aim of this study was to investigate the effects of florfenicol (FLR) on immune defense parameters, antioxidant status and biomolecule damage of the white shrimp Litopenaeus vannamei. In this study, juvenile shrimp (9.5 ± 0.5 cm) were fed coated with FLR 100 mg kg− 1 and 200 mg kg− 1 body weight for 6 days followed by a period of feeding without antibiotic for 10 days. Hemolymph and hepatopancreas were collected on the 3rd and 6th day of feeding the antibiotics and at 1, 3, 6 and 10 days after FLR withdrawal. Results showed there were no significant differences in proPO activity in hemocytes, α2-macroglobulin (α2-M) and antibacterial activities in plasma between 100 mg kg− 1 FLR treatment and control group, while 200 mg kg− 1 FLR treatment suppressed all of them (P < 0.05), and both treatment significantly decreased the total hemocyte count (THC) and phagocytic activity in a dose-dependent manner. Results also showed that 100 mg kg− 1 FLR treatment significantly increased superoxide dismutase (SOD) activity, while 200 mg kg− 1 FLR treatment suppressed it. Moreover, FLR had a suppressive effect on antioxidant status of T-AOC, GSH contents and GSH/GSSG ratio. Additionally, FLR can cause biomolecule damage, such as decreased the F value and increased the levels of malondialdehyde (MDA) and protein carbonyl (PC) contents. The present results suggest that FLR can affect the physiological health of L. vannamei, and these results will provide scientific datas for antibiotic safety evaluation.